3/5/2013 10:00 AM PST

Carly Rae Jepsen has officially pulled out of a HUGE concert for the Boy Scouts of America ... claiming she wants no part of an organization that doesn't support gay rights.

The "Call Me Maybe" singer had been booked to perform at the National Scout Jamboree in Mount Hope, West Virginia in July, along with the band Train.

But moments ago, Jepsen tweeted that she's yanked herself from the festival ... squarely because of the group's ban on openly gay scouts and scout leaders.

"As an artist who believes in equality for all people, I will not be participating in the Boy Scouts of America Jamboree this summer," Jepsen said.

She continued, "I always have and will continue to support the LGBT community on a global level ... and stay informed on the ever changing landscape in the ongoing battle for gay rights in this country and across the globe."

FYI -- Train has also backed out of the show ... but says they will be happy to re-join the show IF the Boy Scouts reverse their anti-gay policy.